This invention relates to an automatic engine stop-restart system, and particularly to an automatic engine stop-restart system wherein automatic stop of an engine is prevented under predetermined conditions, so that operation of a vehicle can be facilitated.
In general, there are many cases where, during driving of a motor vehicle, the motor vehicle is required to be temporarily stopped due to various causes including a traffic jam and a red traffic light. In the case of temporary stop as described above, it is the common practice that, until the motor vehicle can move again, the motor vehicle is in the waiting state, idling the engine. When the temporary stops as described above are frequent, the fuel consumption rate is deteriorated and it is unfavorable from the viewpoint of the emission control. Then, each time of the temporary stop, the engine is manually stopped by means of a key switch, and, in moving the vehicle, the engine is manually started, thus enabling to solve the above-described problem. However, these manual operations suffer from low controllability and it is not favorable from the viewpoint of the safety control.
In view of the above-described facts, there has been proposed an automatic engine stop-restart system (hereinafter referred to as "EASS") wherein, in temporarily stopping the motor vehicle, the engine is automatically stopped, and thereafter, the engine is automatically restarted. In this EASS, for example, a status signal of a clutch pedal, an engine rotational speed signal, a vehicle speed signal, a water temperature signal, an oil pressure signal and other signals are taken in an electronic control circuit mainly consisting of a microcomputer. When conditions of stopping the engine are fulfilled, the functions of ignition means and a fuel system are stopped to thereby stop the engine annd when conditions of rotatably starting the engine are fulfilled, a starter is rotated to start the engine, so that the rotation of the engine can be maintained.
The engine is not automatically stopped in the following cases from the viewpoint of safety. (i) When the temperature of engine cooling water is lower or higher than a predetermined temperature, restart of the engine becomes difficult, and consequently, the engine is not stopped. (ii) While head lamps, a wiper and the like are used, electrical load is heavy, and consequently, the engine is not stopped. (iii) At the time of right turn, the engine is not stopped. Further, (iv) While an air conditioner is used, similarly, the engine is not stopped.
The use condition of the wiper in Item (ii) is divided into two including one use of the wiper in a high speed motion and the other use in a low speed motion, and hence, heretofore, there has been need to reliably detect the use of the wiper irrespective of the motions. Therefore, there has been practised that, based on utilization of a wiper motor during the use of the wiper, voltage signals from a high (high speed motion) terminal and a low (low speed motion) terminal of the wiper motor are taken into a control circuit, whereby the state of the wiper has been detected by the respective voltage signals. However, the above-described method has presented the disadvantages that two signal lines are required for the high speed motion and low speed motion and also two input ports are needed in the control circuit.